The relationship between some perennial desert plants originated in different phytogeographical regions and proline concentration

Proline accumulates in plants under osmotic stress. This study considers whether or not plants from the arid Saharo-Arabian phytogeographical region, contain more proline than those that originated in the more humid Irano-Turanian region, based on the assumption that, under drier conditions, overproduction of proline has been selected in some species as a mechanism for osmoregulation. In a comparison between 2 summer semideciduous species that have a Saharo-Arabian (Zygophyllum dumosum) or Irano-Turanian (Artemisia herba-alba) chorotype, the former had significantly more leaf proline. Comparison between 2 summer deciduous half-shrub species, Helianthemum ventosum (Saharo-Arabian) and H. vesicarium (Irano-Turanian) showed a higher proline concentration in the former. Only Z. dumosum showed a high proline concentration throughout the year; hence, it is possible that, in this species, proline may play a more important role in osmoregulation than in the others. -Authors